Swellable Seal with Backup

ABSTRACT

A well seal assembly for use in a seal groove of a well component. The seal assembly including a swellable elastomer seal to reside in the seal groove. The swellable elastomer seal responsive to expand when in contact with a specified fluid. A backup member is provided to reside in the seal groove, axially between the swellable elastomer seal and an axial end wall of the seal groove. The backup ring includes an undulation that, when axially compressed, expands the backup member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase Application under 35 U.S.C.§371 and claims the benefit of priority to International ApplicationSerial No. PCT/US2013/068776, filed on Nov. 6, 2013, the contents ofwhich are hereby incorporated by reference.

BACKGROUND

The present disclosure relates to well tools that utilize swellableseals.

Downhole conditions in a well present numerous sealing challenges. Forexample, seals in a well must often withstand extended exposure to highpressures and temperature. In such conditions, commonly used elastomerseals tend to extrude into the gap between the component carrying theseal and the surface sealed against, and ultimately fail. Complex backupring designs have been developed to address this problem, by bridgingthe gap and supporting the extrusion against extrusion. However, thebackup ring designs are actuated only when the seals are pressurized.Also, in the context of a stinger or stab, where one well component issealed in a bore of another well component, multiple seals and thusmultiple backup rings are used. To accommodate the multiple seals in asmall space, O-rings or chevron seals are used. However, theeffectiveness of such seals is dependent to the cleanliness and surfacefinish of the surface sealed against.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic side view of a well incorporating a tubing string.

FIG. 2 is an side cross-sectional view of an example of two wellcomponents incoporporating a sealing assembly.

FIGS. 3A and 3B are detail views of the example well components, showingan end of the sealing assembly prior to the seal swelling and after theseal has swelled.

FIG. 4 is a perspective view of an example backup member showing theundulations.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Referring first to FIG. 1, a well includes a substantially cylindricalwellbore 10 that extends from a wellhead 22 at the surface 12 downwardinto the Earth into one or more subterranean zones of interest 14 (oneshown). The subterranean zone 14 can corresponding to a singleformation, a portion of a formation, or more than one formulationaccessed by the well, and a given well can access one or more than onesubterranean zone 14. In certain instances, the formations of thesubterranean zone are hydrocarbon bearing, such as oil and/or gasdeposits, and the well will be used in producing the hydrocarbons and/orused in aiding production of the hydrocarbons from another well (e.g.,as an injection or observation well). The concepts herein, however, areapplicable to virtually any type of well. A portion of the wellbore 10extending from the wellhead 22 to the subterranean zone 14 is lined withlengths of tubing, called casing 16.

The depicted well is a vertical well, extending substantially verticallyfrom the surface 12 to the subterranean zone 14. The concepts herein,however, are applicable to many other different configurations of wells,including horizontal, slanted or otherwise deviated wells, andmultilateral wells.

A tubing string 18 is shown as having been lowered from the surface 12into the wellbore 10. The tubing string 18 is a series of jointedlengths of tubing coupled together end-to-end and/or a continuous (i.e.,not jointed) coiled tubing, and includes one or more well tools (e.g.,one shown, well tool 20). The string 18 has an interior, center borethat enables communication of fluid between the wellhead 22 andlocations downhole (e.g., the subterranean zone 14 and/or otherlocations). In other instances, the string 18 can be arranged such thatit does not extend from the surface 12, but rather depends into the wellon a wire, such as a slickline, wireline, e-line and/or other wire.

The concepts herein apply to a sealing arrangement that can be used in anumber of different contexts to seal between well components in a well.For example, the sealing arrangement can be used in the well tool 20. Incertain instances, the well tool 20 is of a type having an inner tubingcomponent nested in an outer tubing component, with the sealingarrangement described herein configured to seal between the tubings. Thesealing arrangement, however, need not be limited to sealing componentsof the same tool or device. For example, in certain instances, the welltool 20 is a packer type tool (e.g., packer, bridge plug, frac plugand/or other) that has the sealing arrangement configured to seal thetool 20 to the inner surface of the casing 16, a liner or othercomponent in the well to seal the annulus around the tubing string 18.In another example, the tubing string 18 can be placed in the well intwo parts, with an uphole component that has a stab or stinger that isreceived into a corresponding bore of the downhole component. In thisinstance, the sealing arrangement is configured to seal to the bore ofthe other component, and thus seal between the two tubings. In yetanother example, a running tool or actuating tool can be used to operatethe well tool 20 or another component in the well. In this instances,the running or actuating tool has a stinger or stab that is receivedinto a corresponding bore of the tool or device being actuated, and thesealing arrangement is configured to seal between the stinger/stab andbore. Other examples exist and are within the concepts herein.

Referring to FIG. 2, two well components 30, 32 are shown in a half sidecross-sectional view. In the present example, the well components 30, 32are two elongate tubings (e.g., tubings of a well tool, a packer andcasing, a stinger and bore, or other), concentrically nested within eachother. The inner tubing (component 32) includes a seal groove 24 sizedto receive an elongate swellable elastomer seal 26 and backup members28. Each of the seal groove 24, swellable seal 26 and backup members 28are annular or ring shaped to encircle the tubular well components 30,32. An annular gap 34 is formed between the well components 30, 32.Although described herein in connection with tubular well components,the same concepts could be applied to non-cylindrical, flat or othershapes. Thus, the seal 26, backup members 28 and other aspects need notbe annular.

The elongate swellable elastomer seal 26 is made from a swellableelastomer that swells or expands on contact with a specified fluid,e.g., oil, water, and/or other. Notably, the swellable elastomer swellsin all directions uniformly, unless constrained. Therefore, in theexample with the annular swellable elastomer seal 26 in the seal groove24, the seal 26 swells radially outward, as well as axially within thegroove 24, parallel to centerline of the well components 30, 32. Theseal 26 is elongate in that it axial dimension is longer than its radialdimension, but other configurations of seal 26 could be provided. Incertain instances, the radial dimension of the seal 26 is selected toprovide a gap with the component 30 to allow the seal 26 (and component32) to be inserted and withdrawn from component 30.

A backup member 28 is provided at each end of the seal 26, axiallybetween the seal 26 and opposing axial ends of the seal groove 24. Inother instances, only one backup member 28 is provided. The backupmember 28 is a wave backup member made as a wave spring, or configuredsimilarly to a wave spring, with one or more axial undulations 36distributed around the backup member 28. In certain instances, theundulations can be distributed evenly around the backup member 28, forexample, as in FIG. 4 showing four undulations 36 distributed at 90°from each other. Although shown as smooth, curving sine wave likeundulations 36, the undulations could be more abrupt and/or a differentshape. The backup member 28 is constructed of a thin, flat material withparallel sidewall surfaces, and the undulations 36 are configured sothat when the member 28 is axially compressed toward flat, they expandthe backup member 28 circumferentially, and correspondingly radiallyoutward. In certain instances, the backup member 28 can be sized tolightly contact or provide a gap with the component 30 in an unexpanded(not axially compressed) free state. Such a configuration allows thebackup member 28 to slide axially through the component 30 without muchor any resistance, allowing the component 32 to be inserted andwithdrawn into the component 30. The number and amplitude A of theundulations 36 can be selected so that when the backup member 28 iscompressed, it bridges the gap 34 and abuts and presses on the component30. The number of undulations 36 and the amplitude A of the undulationscan be selected to provide a contact pressure against the component 30to provide an adequate degree of backup that prevents the swellable seal26 from extruding through gap 34. In certain instances, the backupmember 28 is provided with a chamfer 38 on its inner diameter orientedtoward the seal 26 to facilitate the member 28 expanding and centeringon the seal 26.

The backup member 28 can be constructed of a number of differentmaterials. In certain instances, the member 28 can be constructed of amaterial having a higher hardness and/or yield strength than theelastomer of the swellable seal 26 to facilitate the backup member 28providing an effective backup. In certain instances, the material isselected based on its ability to survive the high, downholetemperatures. Some example materials for the backup member includemetal, polymer, composite and/or other materials or mixes of materials.

In operation, with the components 30, 32 residing in the well and thebackup members 28 and seal 26 residing in the seal groove 24, theswellable seal 26 is contacted with the specified fluid. The seal 26responds by swelling into contact and sealing to the component 30. Incertain instances, the seal formed by the seal 26 is gas tight. FIG. 3Ais a detail view about the axial end of the seal groove 24, showing theswellable elastomer seal 26 prior to swelling and the backup 28unexpanded. When the swellable elastomer seal 26 is in contact with thespecified fluid, it swells and expands both radially and axially. Inaxially expanding, the swellable elastomer seal 26 compresses the backupmembers 28 against the axial end wall of the seal groove 24. Theundulations of the backup members 28 axially compress, and cause thebackup members 28 to expand radially into abutting contact with thecomponent 30, as shown in FIG. 3B. Then, as the seal 26 begins to hold apressure differential, the seal 26 is supported against extrusionthrough the gap 34 by the low pressure side backup member 28 pressingagainst the component 30. By providing two backup members 28, thepressure differential can be reversed and the opposing backup member 28will support the seal 26 against extrusion through the gap 34.

Notably, by using a swellable elastomer seal 26, the surface finish ofthe surface sealed against on the component 30 need not be tightlycontrolled, as the swellable seal 26 provides a contact pressure thatfacilitates sealing rougher surfaces than non-swelling seals. In thecontext of a stinger or stab, the component 30 need not be provided witha polished bore receptacle. Also, the seal 26 can provie more surfacearea for sealing than a conventional O-ring or chevron seal. In certaininstances, the greater surface area and/or the contact pressure fromswelling will allow the swellable seal 26 to seal, even if damaged.Because the seal 26 swells in contact with fluid, a pressuredifferential is not necessary to achieve a seal or to actuate the backupmembers 28 into supporting the seal 26. The swelling also facilitatesinsertion of the component 32 into component 30, because the seal 26need not contact component 30 until in contact with the specified fluid.Once sealing, the seal 26 resists withdrawal of the component 32 fromcomponent 30. In certain instances, because of the simplicity of thebackup members 28, the cost to manufacture can be less than other morecomplex backups and chevron seals.

A number of embodiments have been described. Nevertheless, it will beunderstood that various modifications may be made. Accordingly, otherembodiments are within the scope of the following claims.

What is claimed is:
 1. A well seal assembly for use in a seal groove ofan elongate well component, comprising: a swellable elastomer seal toreside in the seal groove, the swellable elastomer seal responsive toexpand when in contact with a specified fluid; and a backup member toreside in the seal groove axially between the swellable elastomer sealand an axial end wall of the seal groove, the backup member comprisingan undulation that, when axially compressed, expands the backup member.2. The well seal assembly of claim 1, where the backup member comprisesa plurality of axial undulations distributed evenly around the backupmember.
 3. The well seal assembly of claim 1, where the backup membercomprises a wave spring.
 4. The well seal assembly of claim 1, where theswellable elastomer seal swells axially when in contact with thespecified fluid and axially compresses the backup member.
 5. The wellseal assembly of claim 1, where the well component comprises a firsttubular and the seal groove is annular to encircle the first tubular,and the first tubular of the well component is insertable into aspecified second tubular; and where the swellable elastomer seal isannular to encircle the first tubular and swellable to abut and sealagainst the second tubular.
 6. The well seal assembly of claim 5, wherethe backup member is annular to encircle the first tubular and expandsradially, when axially compressed, to press against the second tubular.7. The well seal assembly of claim 1, comprising a second backup memberto reside in the seal groove axially between the swellable elastomerseal and an opposite axial end wall of the seal groove.
 8. The well sealassembly of claim 1, where the backup member comprises a chamferoriented toward the swellable elastomer seal.
 9. The well seal assemblyof claim 8, where the backup member comprises parallel, opposing axialsidewalls.
 10. The well seal assembly of claim 1, where the backupmember is a different, harder material than the swellable elastomerseal.
 11. A method, comprising: expanding, in response to contact with aspecified fluid, a swellable elastomer seal in a seal groove of anelongate well component; and axially compressing an undulation of abackup member in the seal groove with the swellable elastomer seal,expanding the backup member outward.
 12. The method of claim 11, whereaxially compressing an undulation of the backup member comprises axiallycompressing a plurality of axial undulations of the backup member, theundulations distributed evenly around the backup member.
 13. The methodof claim 11, where axially compressing an undulation of the backupmember comprises axially compressing the undulation between the seal andan axial end wall of the seal groove.
 14. The method of claim 11,comprising sealing, with the swellable elastomer seal, against a surfaceof a second well component; and supporting the swellable elastomer sealagainst extruding through a gap between the first mentioned wellcomponent and the second well component with the backup member.
 15. Themethod of claim 11, comprising axially compressing an undulation of asecond backup member in the seal groove with the swellable elastomerseal, expanding the second backup member outward.
 16. The method ofclaim 15, comprising sealing, with the swellable elastomer seal, againsta surface of a second well component; and supporting the swellableelastomer seal against extruding through gaps between the firstmentioned well component and the second well component with the firstmentioned backup member and the second backup member.
 17. A well devicefor use in a well, comprising: a swellable seal in a seal groove of thewell device, the swellable seal responsive to swell when in contact witha fluid; and a wave backup ring in the seal groove responsive to expandoutward when axially compressed by the swellable seal.
 18. The welldevice of claim 17, where the wave backup ring comprises a plurality ofaxial undulations distributed evenly around the ring.
 19. The welldevice of claim 17, where the wave backup ring comprises a chamferoriented toward the swellable seal.
 20. The well device of claim 17,comprising a second wave backup ring in the seal groove opposite theswellable seal and responsive to expand outward when axially compressedby the swellable seal.